Abstract
ABSTRACT We investigated the early life growth pattern of pacamã, Lophiosilurus alexandri , a catfish endemic to the rio São Francisco basin, Brazil. Pacamã larvae were kept in a galvanized trough for 29 days after hatching. We collected approximately 10 larvae daily (total number = 285). We obtained from each specimen the total length (independent variable) and 11 other body measurements (dependent variables). We performed linear regressions on the log-transformed data to determine the growth pattern of the body measurements and the respective inflexion point on the growth curves. Except for trunk length, trunk width and yolk sac volume, the remaining body measurements showed a positive allometric growth coefficient up to the respective IP followed by a decrease in the rate of relative growth afterwards. Although trunk width presented a positive allometric growth, no significant inflexion point was detected. The dorsal-ventral head flattening seen in the adult pacamã was quickly expressed in the larvae as indicated by the large allometric growth of head width. Maxillary barbels showed the highest growth rate. The exceptionally high growth rates of eyes and maxillary barbels and the acquired ability to capture prey (as suggested by mouth length growth) strengthened the hypothesis of growth priorities in which the most essential organs develop first.
Highlights
During early life of fishes, changes in growth rates occur, namely in the development of structures related to sensorial perceptions, gas exchange, swimming, and capture of food that result in abilities to overcome the hostile environment (Osse & van den Boogaart, 1995; van Snik et al, 1997; Gisbert, 1999; Kupren et al, 2014)
We expanded the previous work of GuimarãesCruz et al (2014) on early growth of pacamã, Lophiosilurus alexandri Steindachner, 1876, to incorporate analyses of inflexion point (IP) of different larval body measurements
We examined circa 10 larvae/day, from day 0 to the 29th day after hatching (DAH) collected for a previous study (Guimarães-Cruz et al, 2009)
Summary
During early life of fishes, changes in growth rates occur, namely in the development of structures related to sensorial perceptions, gas exchange, swimming, and capture of food that result in abilities to overcome the hostile environment (Osse & van den Boogaart, 1995; van Snik et al, 1997; Gisbert, 1999; Kupren et al, 2014). The point where growth rates change (inflexion point, IP) can be a valuable indicator for transitions in the ecology of an organism and thereby helps to detect transitions in the ontogeny (Safran, 1992). Knowledge of these changing relationship between larva and environment is very useful in conservation and is likely important for fisheries and aquaculture management (Koumoundouros et al, 1995). We expanded the previous work of GuimarãesCruz et al (2014) on early growth of pacamã, Lophiosilurus alexandri Steindachner, 1876, to incorporate analyses of IPs of different larval body measurements
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